{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,8]],"date-time":"2026-09-08T14:10:48Z","timestamp":1788876648981,"version":"build-2803163510"},"reference-count":39,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2026,9,8]],"date-time":"2026-09-08T00:00:00Z","timestamp":1788825600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Tibet University","award":["2026-GSP-017"],"award-info":[{"award-number":["2026-GSP-017"]}]},{"award":["2026-GSP-017"],"award-info":[{"award-number":["2026-GSP-017"]}],"id":[{"id":"https:\/\/ror.org\/05petvd47","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Research on Mechanical Properties and Design Methods of Concrete Composite Structures with Biomass Green Composite Materials under High-Altitude Environment","award":["XZ202601ZR0125"],"award-info":[{"award-number":["XZ202601ZR0125"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Fiber reinforced polymers (FRPs) have gained widespread application in civil engineering due to their light weight, high strength, and excellent corrosion resistance. Among various fibers, natural fibers have recently attracted increasing attention because of their renewability, low cost, and reduced environmental impact. However, natural fiber reinforced polymer composites (NFRPs) suffer from high moisture absorption and inferior mechanical properties, which are further deteriorated under hygrothermal environments, severely limiting their service conditions. This study focuses on flax fiber reinforced polymer composites (FFRPs) and, through systematic experimental testing, investigates their durability under hygrothermal conditions. Hygrothermal aging was conducted at 90% relative humidity and 40 \u00b0C for up to 30 days. Water uptake, mechanical properties, and thermomechanical behavior were evaluated for composites fabricated by two molding processes (autoclave and hand-laying) with varying ply numbers (10, 20, 30, 40, and 50 layers). The optimal ply number for mechanical performance was identified, and the influence of the different resin systems and fiber forms between the two processes on the cross-process comparison, as well as the rationale for the 30-layer laminate and the effect of laminate thickness, were clarified. Microstructural changes were examined via scanning electron microscopy. This work provides systematic experimental evidence and data for assessing the long-term durability of FFRP composites in humid and warm environments, offering valuable guidance for their practical application in civil infrastructure.<\/jats:p>","DOI":"10.3390\/ma19183822","type":"journal-article","created":{"date-parts":[[2026,9,8]],"date-time":"2026-09-08T13:46:33Z","timestamp":1788875193000},"page":"3822","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Durability of Flax Fiber Reinforced Polymer Sheets Under Hygrothermal Conditions: Tensile and Shear Performance"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0009-0003-0218-7550","authenticated-orcid":false,"given":"Yangyang","family":"Xia","sequence":"first","affiliation":[{"name":"College of Engineering, Xizang University, Lhasa 850000, China"},{"name":"Plateau Major Infrastructure Smart Construction and Resilience Safety Technology Innovation Center, Lhasa 850000, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"supervision","vocabulary":"credit"}]},{"given":"Pengyu","family":"Li","sequence":"additional","affiliation":[{"name":"College of Engineering, Xizang University, Lhasa 850000, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-original-draft","vocabulary":"credit"}]},{"given":"Lingli","family":"Shen","sequence":"additional","affiliation":[{"name":"College of Engineering, Xizang University, Lhasa 850000, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"}]},{"given":"Jifang","family":"Niu","sequence":"additional","affiliation":[{"name":"College of Engineering, Xizang University, Lhasa 850000, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"investigation","vocabulary":"credit"}]},{"given":"Huiguo","family":"Zhao","sequence":"additional","affiliation":[{"name":"College of Engineering, Xizang University, Lhasa 850000, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"visualization","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,8]]},"reference":[{"key":"ref_1","first-page":"69","article-title":"Application of carbon fiber composite materials in building reinforcement engineering","volume":"1","author":"Hou","year":"2024","journal-title":"Plast. Addit."},{"key":"ref_2","first-page":"1658","article-title":"Research progress of thermoplastic composites reinforced with natural plant fibers","volume":"41","author":"Yang","year":"2024","journal-title":"Fine Chem."},{"key":"ref_3","unstructured":"Li, X. (2022). Study on Ammonia Degumming Treatment of Ramie Fiber and Recyclable Utilization of Black Liquor. [Master\u2019s Thesis, Jinan University]. (In Chinese)."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"112130","DOI":"10.1016\/j.rser.2022.112130","article-title":"Lignocellulosic biomass as renewable feedstock for biodegradable and recyclable plastics production: A sustainable approach","volume":"158","author":"Raj","year":"2022","journal-title":"Renew. Sustain. Energy Rev."},{"key":"ref_5","first-page":"60","article-title":"Research progress of natural plant fiber composites","volume":"42","author":"Gao","year":"2021","journal-title":"J. Northwest Minzu Univ. (Nat. Sci.)"},{"key":"ref_6","first-page":"231","article-title":"Research and application of properties of natural fiber reinforced composites","volume":"49","author":"Li","year":"2021","journal-title":"New Chem. Mater."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"80","DOI":"10.1007\/s11837-006-0234-2","article-title":"Natural-fiber-reinforced polymer composites in automotive applications","volume":"58","author":"Holbery","year":"2006","journal-title":"JOM"},{"key":"ref_8","first-page":"153","article-title":"Research status and development prospect of flax fiber cement-based composites","volume":"26","author":"Zhao","year":"2024","journal-title":"J. Agric. Sci. Technol."},{"key":"ref_9","unstructured":"Shi, G. (2003). Effect of Surface Chemistry on the Interfacial Adhesion and Mechanical Properties of Natural Fiber Reinforced Polymer Composites. [Ph.D. Thesis, Michigan State University]."},{"key":"ref_10","unstructured":"Zhang, X. (2023). Research on Grafting Modification and Tensile Failure Model of Multi-Walled Carbon Nanotubes in Flax Fiber Composites. [Master\u2019s Thesis, Xi\u2019an University of Technology]. (In Chinese)."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1029","DOI":"10.1016\/j.conbuildmat.2015.10.207","article-title":"Effects of elevated temperatures on the mechanical properties of basalt fibers and BFRP plates","volume":"127","author":"Lu","year":"2016","journal-title":"Constr. Build. Mater."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Tu, J., Xie, H., and Gao, K. (2020). Prediction of the Long-Term Performance and Durability of GFRP Bars under the Combined Effect of a Sustained Load and Severe Environments. Materials, 13.","DOI":"10.3390\/ma13102341"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"36","DOI":"10.1016\/j.matpr.2019.12.154","article-title":"Long-term moisture absorption and durability of FRP pultruded rebars","volume":"34","author":"Starkova","year":"2021","journal-title":"Mater. Today Proc."},{"key":"ref_14","first-page":"43","article-title":"Preparation and performance study of lightweight epoxy glass fiber composites","volume":"22","author":"Hong","year":"2024","journal-title":"Chem. Propellants Polym. Mater."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1016\/j.compositesa.2016.04.023","article-title":"Hybridisation effect on diffusion kinetic and tensile mechanical behaviour of epoxy based flax-glass composites","volume":"87","author":"Saidane","year":"2016","journal-title":"Compos. Part A Appl. Sci. Manuf."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"115566","DOI":"10.1016\/j.compstruct.2022.115566","article-title":"Research on mechanical properties and durability of flax\/glass fiber bio-hybrid FRP composites laminates","volume":"290","author":"Liu","year":"2022","journal-title":"Compos. Struct."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1617\/s11527-022-01988-8","article-title":"The immediate and short-term degradation of the wood surface in a cement environment measured by AFM","volume":"55","author":"Li","year":"2022","journal-title":"Mater. Struct."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1601","DOI":"10.1021\/acs.biomac.1c01397","article-title":"Effects of thermal aging on the adhesion forces of biopolymers of wood cell walls","volume":"23","author":"Li","year":"2022","journal-title":"Biomacromolecules"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"284","DOI":"10.1016\/j.compositesb.2019.05.032","article-title":"Environmental effects on the durability and the mechanical performance of flax fiber\/bio-epoxy composites","volume":"171","author":"Moudood","year":"2019","journal-title":"Compos. Part B Eng."},{"key":"ref_20","first-page":"608","article-title":"The influence of moisture absorption on the mechanical properties of unidirectional flax fiber composites","volume":"39","author":"Jia","year":"2022","journal-title":"Acta Mater. Compos. Sin."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"323","DOI":"10.1177\/0731684418818893","article-title":"Flax fiber and its composites: An overview of water and moisture absorption impact on their performance","volume":"38","author":"Moudood","year":"2019","journal-title":"J. Reinf. Plast. Compos."},{"key":"ref_22","first-page":"177","article-title":"Research on mechanical properties of interference connection structures of aviation composite materials in hygrothermal service","volume":"16","author":"Qiu","year":"2025","journal-title":"Adv. Aeronaut. Sci. Eng."},{"key":"ref_23","unstructured":"Zhang, O., Li, C., Niu, Y., Tian, J., Xian, G., and Guo, R. (2024). Study on moisture absorption and interfacial properties of fiber reinforced composites under hygrothermal environment. Compos. Sci. Eng., 87\u201396. (In Chinese)."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"111876","DOI":"10.1016\/j.compstruct.2020.111876","article-title":"An empirical model to predict the strength degradation of the hygrothermal aged CFRP material","volume":"236","author":"Nandagopal","year":"2020","journal-title":"Compos. Struct."},{"key":"ref_25","first-page":"1","article-title":"Damage Mechanisms and Durability Prediction of Carbon Fiber Reinforced Polymer Composites in Plateau Environments","volume":"44","author":"Li","year":"2025","journal-title":"Acta Mater. Compos. Sin."},{"key":"ref_26","first-page":"56","article-title":"Changes of Tg of T300\/BHEP Composite in Thermo-Oxidative, Hygrothermal and Hot Water Aging Conditions","volume":"41","author":"Zhan","year":"2011","journal-title":"Aerosp. Mater. Technol."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1328","DOI":"10.1002\/app.22095","article-title":"Water absorption mechanism and some anomalous effects on the mechanical and viscoelastic behavior of an epoxy system","volume":"99","author":"Papanicolaou","year":"2006","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"314","DOI":"10.1007\/s10853-013-7707-9","article-title":"Synergistic effect of cyclic mechanical loading and moisture absorption on the bending fatigue performance of carbon\/epoxy composites","volume":"49","author":"Zhang","year":"2014","journal-title":"J. Mater. Sci."},{"key":"ref_29","first-page":"24","article-title":"Research on Longitudinal Tensile Properties of Basalt Fiber Reinforced Composite Mesh in Hot and Humid Environment","volume":"4","author":"Yang","year":"2024","journal-title":"Fujian Build. Mater."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Stejskal, M., Sedlacek, F., Spacek, O., Bednarova, N., and Krystek, J. (2025). Towards Sustainable Composite Structures: Experimental Characterisation and Damage Modelling of Unidirectional Flax Fibre-Reinforced Polymers. Polymers, 17.","DOI":"10.3390\/polym17222985"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1975","DOI":"10.1007\/s10443-024-10296-z","article-title":"Environmentally Resistant Flax Fiber-Reinforced Composites for Aircraft Applications: Aviation Stress Tests with Optical and Mechanical Analyses","volume":"32","author":"Schulte","year":"2025","journal-title":"Appl. Compos. Mater."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Parodo, G., Sorrentino, L., Turchetta, S., and Moffa, G. (2024). Manufacturing of Sustainable Composite Materials: The Challenge of Flax Fiber and Polypropylene. Materials, 17.","DOI":"10.3390\/ma17194768"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Martinez, P., and Nutt, S. (2024). Flax\u2013Reinforced Vitrimer Epoxy Composites Produced via RTM. J. Compos. Sci., 8.","DOI":"10.3390\/jcs8070275"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"278","DOI":"10.21741\/9781644903735-32","article-title":"Comparative Study of Autoclave Thermoforming and Hot-Press Moulding for Manufacturing Green Composite Parts","volume":"57","author":"Parodo","year":"2025","journal-title":"Mater. Res. Proc."},{"key":"ref_35","unstructured":"(2020). Standard Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials (Standard No. ASTM D5229\/D5229M-20)."},{"key":"ref_36","unstructured":"(2022). Standard Test Method for Water Absorption of Plastics (Standard No. ASTM D570-22)."},{"key":"ref_37","unstructured":"(2017). Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials (Standard No. ASTM D3039\/D3039M-17)."},{"key":"ref_38","unstructured":"(2022). Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their Laminates (Standard No. ASTM D2344\/D2344M-22)."},{"key":"ref_39","unstructured":"(2015). Standard Test Method for Glass Transition Temperature (DMA Tg) of Polymer Matrix Composites by Dynamic Mechanical Analysis (DMA) (Standard No. ASTM D7028-07)."}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/19\/18\/3822\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,8]],"date-time":"2026-09-08T13:48:22Z","timestamp":1788875302000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/19\/18\/3822"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,8]]},"references-count":39,"journal-issue":{"issue":"18","published-online":{"date-parts":[[2026,9]]}},"alternative-id":["ma19183822"],"URL":"https:\/\/doi.org\/10.3390\/ma19183822","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,8]]}}}